Nati-anal Airlines

Joshua Alper's 1978 book, The Documentary Record of an Infringement, documents his "pseudovandalist" alteration of a damaged billboard to make it read "anal Airlines."

Pre-alteration and damage, the billboard was for National Airlines, which is now defunct.

The book is quite rare, but you can get a copy for $100.

I haven't been able to find a picture of the billboard post-alteration, and I'm not going to pay the money for his book.